Warren Buffett's conglomerate Berkshire Hathaway reported a larger second-quarter profit on Friday, as favorable investment results and strength in the rail and manufacturing businesses offset another underwriting loss in insurance.

The 80-year-old Oracle of Omaha warned in April that the insurance business was probably going to post an underwriting loss for the year because of the severe earthquakes in Japan and New Zealand in the first quarter.

Berkshire reported a net profit of $3.42 billion, or $2,072 per share, compared with a year-earlier profit of $1.97 billion, or $1,195 per share.

Book value per share, Buffett's preferred measure of the conglomerate's worth, rose 3.4 percent to $98,716 per Class A-equivalent share.

The company owns dozens of businesses, from railroads and manufacturing companies to insurance and sweets.

(Reporting by Ben Berkowitz, editing by Matthew Lewis)